As a result of using a polymer shell or film or sheet, monolayer, bilayer, or multilayer, (hereinafter referred to as "membrane") that is defined by (i) having the property of either transporting water vapor at a rate of between about 50 up to about 1000 g/m.sup.2 /day at about 25.degree. C. and at about 50% relative humidity at about atmospheric pressure and/or having an air transport rate of 100-20,000 Gurley seconds (Gs) and (ii) a thickness in the range of from about 0.01 mils up to about 20 mils, our invention provides volatile substance-emitting apparatus and methods for producing same and for using same wherein the volatile substance can be an air freshener, standard aromatizing materials, odor maskants, insecticides, insect repellents, animal repellents, compositions for the evaluation of olfactory functioning in humans, herbicides, pheromones and the like. These volatile substances have previously been used with the following delivery systems:
aerosols; PA0 gels; PA0 paper; PA0 felt; PA0 large pore polymers; PA0 powders; PA0 candles; and PA0 wick-containing liquids. PA0 (i) contained totally within the inner void of the thin shell a volatile composition (which may optionally be temporarily entrapped in an entrapment material and totally entrapped in the entrapment material at least at the instant in time of commencement of the functional operation of the structure--that is, when it is removed from an air-tight package); and PA0 (ii) at least a finite section of said thin shell comprising a porous polymer that is defined by (i) the property of either transporting water vapor at a rate of between about 50 up to about 1000 g/m.sup.2 /day at about 25.degree. C. and at about 50% relative humidity at about atmospheric pressure and/or having an air transport rate of 100-20,000 Gurley seconds (Gs); and (ii) a thickness in the range of from about 0.1 mils up to about 20 mils (e.g., a filled porous polymer containing embedded therein a plurality of finite solid particles) said porous polymer having a porosity such that when said hollow totally enclosed structure is located in an ambient environment said volatile material molecules are either (a) adsorbed onto the inner surface of the microporous polymer section and desorbed from the microporous polymer from the outer surface of the shell at a substantially constant mass flow rate both of the individual volatile components and totally flowing through such porous polymer section, or (b) transported through the porous polymer shell section by means of capillary action at a substantially constant mass flow rate both of the individual volatile components and totally flowing from said thin shell the driving force of such molecular transport resulting from a difference in concentration of volatile substance between: PA0 (1) The property of transporting water vapor at a rate of between about 50 up to about 1000 g/m.sup.2 /day at about 25.degree. C. and at about 50% relative humidity at about atmospheric pressure; PA0 (ii) Porosity range: 100-20,000 Gurley seconds; PA0 (iii) Most preferred porosity range: 8,000-12,000 Gurley seconds; PA0 (iv) Range of Temperature for Operation: -80.degree. C. up to 150.degree. C.; PA0 (v) Most preferred temperature range of Operation: 0.degree. C.-60.degree. C.; and PA0 (vi) A thickness in the range of from about 0.01 mils up to about 20 mils.
With the exception of aerosols, the concentration and rate of release of volatile substance, e.g., perfume, into the atmosphere surrounding the container or emitting apparatus has been a function of the rate of evaporation of volatile material which, in turn, has been a function of the remaining concentration of volatile material in the container or emitting apparatus. Accordingly, the rate of mass transfer (e.g., diffusion in certain instances) of the volatile substance into the surrounding atmosphere has, in the prior art, been "first order", that is, a function of the concentration previously present, e.g.: EQU (dc)/(dt)=kc
wherein c represents concentration of volatile material and k represents a constant.
Furthermore, with respect to the apparatus of the prior art there has been no practical way for ascertainment by the user as to whether or not the bulk of the volatile material has been depleted at a particular point in time. In all instances it is impossible to determine precisely when the volatile substance is no longer being discharged in an effective quantity and/or concentration per unit time into the atmosphere surrounding the container. In those situations where an aroma is being emitted, the actual aroma is usually relatively powerful during the emission notwithstanding the rate of emission of active agent and said aroma retains its power even after its practical effect (e.g., air freshening) is deminimis.
Thus, in Japanese Pat. No. J8-0036,515 assigned to Akane Soji K K, printings from which fragrance is gradually emitted are indicated to be produced by a process comprising (1) preparing fragrance-emitting ink compositions by dispersing (a) fragrance-emitting bases prepared by mixing perfume solutions with thermoplastic resins at elevated temperatures to homogenize the mixture, followed by cooling the mixture to separate fine particles of gelled resin in which the perfume is occluded in (b) a solution of film-forming material and (2) printing the base material with this fragrance-emitting ink composition.
Scent-releasing polyurethane foams are shown to be prepared in German published Application 2,945,757 (assigned to the Tenneco Chemical, Inc.). In published Application 2,945,757, it is indicated that a polyurethane foam containing a particulate filler and perfume is prepared by first mixing the filler with the perfume and adding this mixture to a liquid polyol and finally mixing the thus-obtained composition with an organic polyisocyanate, water and a catalyst to produce the resulting foam. It is indicated that the resulting material is used as an air freshener, deodorant, perfume sachet and the like. It is further indicated that the foam releases the perfume at a limited and constant rate. The said published German Application corresponds to U.S. Pat. No. 4,226,944 issued on Oct. 7, 1980.
U.S. Pat. No. 4,247,498 issued on Jan. 27, 1981 discloses a method for preparing a homogeneous microporous cellular polymer structure which evolves perfumes, insect repellents, odor masking agents and the like at a slow and steady rate. The process of U.S. Pat. No. 4,247,498 comprises (i) heating a mixture of a polymer which may be an olefinic polymer, condensation polymer, oxidation polymer or a blend thereof and a "compatible liquid" to a temperature and for a time sufficient to form a homogeneous solution, (ii) forming at substantially the same time a plurality of liquid droplets of substantially the same size in a continuous liquid polymer phase by cooling the solution, (iii) continuing cooling to solidify the polymer, (iv) then at least partially displacing the "compatible liquid" with a perfume, an odor masking agent, an insect repellant or the like. It is indicated at column 15, line 30 of U.S. Pat. No. 4,247,498 that the disclosed system may be used to create a "thin film of about 1 mil or less up to a relatively thick block of thickness of about 21/3 inches".
Japanese published Application J5-5081,655 assigned to Kureha Chemical Industries KK discloses a slow release air aromatizing composition which comprises an aqueous solution of water soluble high molecular weight substance of viscosity 500-30,000 cps such as polyvinyl acetate, carboxymethyl cellulose, sodium alginate, xanthan gum, etc. admixed with an oil soluble perfume or a water soluble perfume.
U.S. Pat. No. 4,145,001 describes a package having plural layers with the quantity of volatile substance such as a deodorizer sandwiched between the layers. The outer layers of the laminate in U.S. Pat. No. 4,145,001 are impermeable to the substance and its vapors, and thus prevent the escape of vapors as long as the package is sealed. Upon opening of the package of U.S. Pat. No. 4,145,001, delamination occurs at the interface between two selected layers such that the volatile substance is covered on one side only by a layer of material which is permeable to the vapors, thereby allowing controlled release of the vapors over a period of time. A process for production of such package is also disclosed in U.S. Letters Pat. No. 4,145,001.
U.S. Pat. No. 4,161,283 issued on July 17, 1979 discloses an article for the slow release of volatilizable substances such as deodorizers, insecticides, repellents and the like, the article being formed from opposed outer and inner wall members joined along their peripheral portions to define a central reservoir portion for receiving and confining a volatile substance. The outer wall in U.S. Pat. No. 4,161,283 comprises a non-porous flexible polymeric sheet material which does not permit bulk flow but allows molecular diffusion therethrough. The inner wall member comprises an impermable barrier layer. Another barrier layer is releasably bonded to the outer wall and prevents escape of volatilizable substance until its removal at the time of desired use. U.S. Pat. No. 4,285,468 issued on Aug. 25, 1981 discloses essentially the same subject matter as U.S. Pat. No. 4,161,283.
Nothing in the prior art, however, discloses the use of a polymeric membrane (shell, film, or sheet, monolayer, bilayer or multilayer) as defined by (i) having the property of either transporting water vapor at a rate of between about 50 up to about 1000 g/m.sup.2 /day at about 25.degree. C. and at about 50% relative humidity at about atmospheric pressure and/or having an air transport rate of 100-20,000 Gurley seconds (Gs); and (ii) having a thickness in the range of from about 0.01 mils up to about 20 mils which gives rise to the novel structure and process for preparing same of our invention wherein a commercially viable structure capable of dispensing at a steady state and at a constant rate, either continuously or discontinuously for discrete periods of time, a volatile composition of matter such as perfume, air freshener, air deodorant or the like.